Display-type refrigerated cases, of the type having an open side, have for many years been used in retail stores to visually display and permit unimpeded removal of food items while maintaining such food items refrigerated. Such refrigerated open-sided cases are frequently used for food items which must be kept chilled to well below ambient temperature and, in some instances, are to maintain food items below freezing. It will be understood, therefore, in the following discussion that reference to refrigerated cases or cabinets will include both freezer- and nonfreezer-type refrigerating units.
Such open-sided refrigerating cabinets are a convenience to the shopper since they avoid the effort and time loss in opening and closing the usual swinging or sliding doors on conventional closed refrigerated display cabinets. However, open-sided cabinets of the aforementioned type have a long-standing problem in that they rather freely permit large amounts of refrigerated air to "spill out" therefrom. This is undesirable in several respects.
First, energy loss resulting from the spill of cold air from the cabinet and its consequent replacement with warm ambient air necessitates a much larger and more costly refrigerating system than would be required for a completely enclosed refrigerated cabinet of comparable cubic space. The compressor motor for such an open-front cabinet may have to be several times more powerful than the corresponding motor for an enclosed cabinet. Accordingly, the cooling system parts for the open-sided cabinet must be larger and hence more costly, both in terms of initial cost and maintenance cost.
Second, cold air spilled from the open-sided refrigerating cabinet in most instances represents a net energy loss in terms of electricity wasted in unnecessary running of the refrigeration machinery thereof. Such cold air spill may, particularly in cold weather, result in a further indirect energy loss in terms of extra fuel required for extra running of the store's furnace to maintain a desired ambient temperature in the store despite the spilled cold air. This energy waste may be regarded as socially undesirable in times of scarce energy supplies and, in any event, represents an extra overhead cost for the store operator, increasing as energy prices rise.
Further, the spill-out of refrigerated air, particularly in large food markets where several refrigerated cabinets including freezers may be located in the same part of the market, creates cold floor conditions near the freezers, which is uncomfortable for customers and personnel and may upset the equilibrium of the thermostats controlling the store's heating and cooling system, resulting in difficulty in maintaining the desired temperature in the rest of the store.
Further, the continuing unrestricted exchange of cooled air spilling from the refrigerated cabinet and warmer ambient air spilling into the cabinet, through the open side thereof, requires more frequent defrosting, and more frequently subjects the stored food to quality degradation due to the warmer temperatures within the cabinet during a defrost cycle.
In partial solution of these problems, U.S. Pat. Nos. 3,241,899 and 3,542,445 (Donker) and U.S. Pat. No. 3,186,185 (Bently) provide a curtain in the form of a flexible roll-up sheet mounted on a refrigerated cabinet adjacent the access opening thereof. When customer access to contents of the cabinet is not required, as when the store is closed, such sheet can be unrolled to cover the access opening and thereby substantially reduce the amount of cool air spilling out of the cabinet through the access opening. In the case of a very wide cabinet, several such sheets may be used in side-by-side relation.
However, when customer access to the contents of the cabinet is required, as when the store is open, for example during the day, such flexible sheet curtain is rolled up leaving the access opening of the cabinet entirely open, as if no curtain were installed. Accordingly, such a roll-up sheet curtain does not solve the foregoing problems when the store is open for business.
It is also known from U.S. Pat. No. 2,041,258 (Mitchell) to provide a conventional, apparently domestic refrigerator with an air-dam curtain of "cellophane" strips, fixed across the access opening of the refrigerator inboard of the hinged door thereof. The upper and lower ends of each cellophane strip are secured by an adhesive strip to an elastic insert, which elastic insert is in turn secured to a transversely extending flexible strip. An adhesive surface on each of the transversely extending strips secures the elastic inserts thereto and permits securement thereof to the top and bottom interior surfaces of the refrigerator closely behind the refrigerator door. Unfortunately, this particular air-dam construction is complicated by the need for elastic material at the end of each cellophane strip and limits access to the refrigerator contents because both ends of the strips are secured, although resiliently, to the corresponding top and bottom walls of the refrigerator cavity. Moreover, the cellophane air-dam is normally hidden behind the door and functions only during those relatively brief and infrequent intervals during which the householder swings open the door to insert or remove a food item. The structure of this prior patent is apparently not intended for and is not a suitable substitute for a commercial open-sided refrigerated food cabinet for grocery stores and the like, to which the present invention is directed.
Accordingly, the objects of this invention include provision of:
A curtain structure for the access opening of a side-opening, display-type, refrigerated food cabinet capable of obstructing air flow into and out of the cabinet, without significantly impeding visibility of food products within the refrigerated cabinet and without significantly impeding physical access to and removal of such food products from the refrigerated cabinet, when in condition for customer access, as during normal business hours of a store or the like.
A curtain structure, as aforesaid, which during hours in which the store is closed and customer access to the interior of the cabinet is not required, provides for interposition of a pair of substantially fully overlapped curtains substantially closing the access opening of the cabinet to doubly impede airflow into and out of such cabinet and wherein said curtains are spaced to provide an air layer acting as a thermal barrier to additionally reduce transfer of heat into the cabinet.
A curtain structure, as aforesaid, constructable of commonly available, lightweight, inexpensive, sheet material, which curtain structure is readily installable on new open-sided refrigerating cabinets during manufacture as well as being readily installable in the field on existing, in-use, side-opening refrigerator cabinets.
Other objects and purposes will be apparent to persons acquainted with apparatus of this general type upon reading the following specification and inspection of the accompanying drawings.